############################################################################
#
#	File:     lindterp.icn
#
#	Subject:  Procedure to interpret and draw L-System strings
#
#	Author:   Ralph E. Griswold
#
#	Date:     May 2, 2001
#
############################################################################
#
#   This file is in the public domain.
#
############################################################################
#
#  This procedure interpreters strings of characters produced by
#  L-Systems and draws them using turtle graphics.
#
############################################################################
#
#  Links:  lindrec, lindgen, turtle
#
############################################################################

link lindrec
link lindgen
link turtle

global size

#  length is the length of line segments and delta is the amount of
#  direction change.

procedure lindterp(x, y, lsys, gener, length, color, fnc)
   local rewrite, delta, axiom, symbols, c

   /size := 500
   /x := size / 2
   /y := size / 2
   rewrite := lsys.rewrite
   axiom := lsys.axiom
   delta := lsys.delta
   /gener := lsys.gener
   /length := lsys.length

#  The table symbols contains definitions for other symbols as
#  string of other characters.  It remains to be seen how this
#  will be represented.  Note also there is a potential for
#  circularity and unbounded recursion.

   symbols := table()				# table of defined symbols

   TReset()
   TGoto(x, y)

   every c := lindgen(!axiom, rewrite, gener) do
      case c of {
         "F":   TDraw(length)			# draw forward
         "f":   TSkip(length)			# skip forward
         "+":   TRight(delta)			# turn right
         "-":   TLeft(delta)			# turn left
         "[":   TSave()				# save state
         "]":   TRestore()			# restore state
						# interpret defined symbol
         default:   lindterp(\symbols[c], length, delta)
         }					# ignore other characters

   WFlush()

   return

end